This invention relates generally to the field of detectors and more specifically to infrared detectors.
An infrared field may be detected using frequency upconversion whereby the infrared field is converted to a visible field. Frequency upconversion is typically achieved by generating the sum frequency of the infrared field and one or more laser drive fields through the use of second-order or third-order nonlinear optical interactions. Frequency upconversion of an infrared field may provide nearly diffraction-limited performance using a continuous wave laser source, and may have satisfactory conversion efficiency when used with a pulsed wave laser source. Conversion efficiency with a continuous wave laser source, however, may be unsatisfactory for many needs.
According to one embodiment of the present invention, detecting radiation includes receiving a first laser drive field at a cell comprising a medium having a number of states. The first laser drive field has a frequency approximately equivalent to a transition frequency between a first state and a second state of the number of states. A second laser drive field having a frequency approximately equivalent to a transition frequency between the first state and a third state of the number of states, and an infrared field having a frequency approximately equivalent to a transition frequency between the third state and a fourth state of the number of states are received. The medium has a transition between the second state and the third state substantially forbidden to support optimal coherence on the transition between the second state and the third state. The infrared field is upconverted to generate a detectable field having a frequency approximately equivalent to a transition frequency between the second state and the fourth state.
Certain embodiments of the present invention may have technical advantages. Some embodiments may benefit from some, all, or none of these advantages. A technical advantage of one embodiment may be that infrared detection occurs with high conversion efficiency with a continuous wave laser source. A phase-coherent atomic system, that is, a phaseonium, may be used to render a material system transparent to resonant laser radiation while retaining desirable nonlinear optical properties associated with the resonant response of the material system. Another technical advantage of an embodiment may be that the technique may be applicable for a broad range of wavelengths from, for example, the near-infrared to the submillimeter spectral regions.
Other technical advantages are readily apparent to one skilled in the art from the following figures, descriptions, and claims. Embodiments of the invention may include none, some, or all of the technical advantages.